Define ice age
A period of time when Earth has permanent ice sheets (like now)
Define Quaternary
The time period in Earth’s history that began about 2.6 million years ago and continues today; includes the Pleistocene and the Holocene epoch
Define Pleistocene
Part of the Quaternary period that started 2.6 million years ago and ended 11,700 years ago
Define Holocene
Part of the Quaternary period that started 11,700 years ago and is still continuing now
Define glacial period
A colder period in Earth’s history
Define inter-glacial period
A warmer period in Earth’s history
What has happened to the Earth’s temperature over the past 2.5 million years?
The temperature has been constantly fluctuating. There are clear cycles which vary more greatly now.
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Regular cycles between glacial periods and inter-glacial periods
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The cycles have become larger over time
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4 degree difference between glacials and inter-glacials 2.5 million years ago, now it is 8 degrees
How often do inter-glacials occur?
They occur on cycles of approximately 100,000 years
What are some significant temperature events from the past 1,500 years?
Medieval warm period (900-1200)
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Warmer weather
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Romans grew grapes in vineyards in South East England
Little Ice Age
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Cold period
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There were ‘Frost fairs’ on the Thames - people went ice skating on the river
What has happened to the temperature since 1880?
There are 3 clear stages:
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1880-1950: an increase of 0.5 degrees
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1950-1980: no real change
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1980-2020: a further rise of 0.5 degrees
This is important as it shows the impact of humans on the climate since the Industrial Revolution
What can ice cores show us
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Scientists can study ice up to 800,000 years old
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Light layers of snow indicate summer (heavier snowfall) and dark layers indicate winter (from all the dust that blows around in winter)
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Scientists look for oxygen 16 and 18, 16 indicates colder weather and 18 indicates warmer
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Large amounts of carbon dioxide in the ice indicate warmer temperatures
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We know this data is reliable as we can match it to ice from more recent times where we also have reliable temperature records from weather stations
What can the amount of sea ice tell us about Earth’s temperature?
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Sea ice is measured by satellite images
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Sea ice maximum is the maximum amount of sea ice in a year (April) and sea ice minimum is the least amount of sea ice during the year (October)
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Area covered by sea ice has decreased by 2 million square km since 1979
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It’s very reliable in terms of area covered by ice - satellites allow us to take exact measurements, however it is difficult to measure the depth - this needs to be done by submarines and they can only cover a small area
How can first hand accounts help us measure the Earth’s temperature?
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They give us anecdotal evidence of what weather conditions were like in the past
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Famous painting: ‘A Frost Fair on the Thames’ - Abraham Hondius
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John Evelyn’s diary entries describe the frost fairs
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They give a good first hand account of weather conditions but are prone to exaggeration - biased
Describe the natural greenhouse effect
Natural greenhouse effect (left side):
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Energy comes from the sun as short wave radiation
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Most energy passes through a layer of naturally occurring greenhouse gases
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Earth’s surface is warmed
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Some energy is reflected back out into space as long-wave radiation
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Long-wave radiation does not pass through greenhouse gases as easily as short-wave radiation
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Some energy escapes back out into space
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Some energy is absorbed by greenhouse gases and some is reflected back to Earth
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Earth is warmed up enough for life to exist
Describe the enhanced greenhouse effect
Enhanced greenhouse effect (right side):
1.
Energy comes from the sun as short wave radiation
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Most energy passes through a layer of naturally occurring greenhouse gases. Human activity has put more greenhouse gases in the atmosphere
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Earth’s surface is warmed
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Some energy is reflected back out into space as long-wave radiation
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Long-wave radiation does not pass through greenhouse gases as easily as short wave radiation
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Some energy escapes back out into space
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The thick layer of greenhouse gases absorbs more energy and more is reflected back to Earth
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Earth becomes warmer. This causes global warming
How has carbon dioxide contributed to the enhanced greenhouse effect?
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60%
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Sources: burning fossil fuels (coal, gas) to make electricity, industry, cars, deforestation
How has methane contributed to the enhanced greenhouse effect?
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15%
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Sources: landfill sites, rice production, farm animals (mainly cows)
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Global warming potential: 25 times
How have halocarbons contributed to the enhanced greenhouse effect?
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15%
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Sources: air conditioning, fridges, aerosols, foam packaging
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Global warming potential: 15000 times
How has nitrous oxide contributed to the enhanced greenhouse effect?
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6%
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Sources: agricultural fertilisers, car exhausts
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Global warming potential: 250 times
What’s the relationship between carbon dioxide concentrations and temperature?
They’re roughly proportional. As carbon dioxide increases, so does the global average temperature.
However, carbon dioxide increases slightly before temperature as carbon dioxide increases the rate of global warming
Which countries are the major carbon emitters?
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China (25%)
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USA (20%)
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Russia, India, Japan, Germany
China accounts for over a quarter of the world’s carbon emissions as they are an industrial powerhouse. 1.3 billion people live in China (1/6 of the world’s population). China is a wealthier country than India so it has higher carbon emissions per capita. People have more money and use more consumer products. Car ownership is higher in China
What are sun spots and how do they affect Earth’s temperature?
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They’re dark spots on the sun’s surface
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They’re temporary and caused by magnetic storms
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They send more solar energy to Earth so they increase the temperature
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Cycles last 11 years
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They have been linked to the Little Ice Age (1300-1870) with fewer sun spots and the Medieval Warm Period (950-1250) with more sun spots
How do volcanic eruptions affect the Earth’s climate?
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They release huge amounts of dust into the atmosphere, the dust blocks sunlight which results in cooler temperatures
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Water vapour is released causing more rainfall locally. However, global rainfall might decrease due to less evaporation
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They’re linked to the Medieval Warm Period (less volcanic activity) and the Little Ice Age (more volcanic activity)
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The Pinatubo eruption in 1991 lead to 1 degree of cooling for 2 years
What are Milankovitch’s three ideas?
Eccentricity (changes in the shape of the Earth’s orbit)
Obliquity (changes in how Earth tilts on its axis)
Precession (the amount the Earth wobbles on its axis)
